Automatic rheostat.



H. M. GROSSMAN & J. WYNN, JR.

AUTOMATIC RHEOS'IAT.

APPLICATION FILED MAR. 25, 1912.

Patented Nov. 18, 1913.

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anuentou Hemp/Y. Gina-17mg John k/ym cfi! UNITED STATES PATENT OFFICE.

mama! u. eaossnm m JOHN WYRN, m, or canon, omo.

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Patented Nov. 18, 1913.

Application filed larch 25, 1912. Serial No. 685,972.

To all whom it mm Be it known t at we, MAN and JOHN WYNN, Jr., citizens of the United States, residing at Canton in the county of Stark and State of Ohio, have invented certain new and useful Improvements in Automatic Rheostats, of which the following is a specification. Our invention relates to improvements in devices for automatically throwing resistance into a circuit, for varying the resistance in accordance with the requirements, and for automatically throwing the resistance entirely out of circuit when certain predetermined conditions are attained.

The invention especially relates to an automatic rheostat for use in the starting and control of electric motors and is especially applicable to motors used for driving air pumps or fans for pneumatic cleaning and the like.

The objects of the invention are to generally improve devices of the character mentioned, to provide a rheostat which will an- COYLGET'IZ.

HENRY M. Gaosstomatically control the resistance in a circuit, as for the control of a motor, to provide an automaticrheostat which will be reliable and easily operated and which is especially applicable to air pressure or vacuum producing machinery and which will be directly actuated by such air pressure or vacuum. objects apparent to those skilled in the art, may be attained by the construction'illustrated in the accompanyin drawings, although the invention may be embodied in other forms, the construction illustrated being[ chosen by way of example.

n the drawings Figure 1 is a vertical sectional view of an automatic rheostat embodying our invention showing ap ropriate connection when the same is used upon a vacuum producing device. Fig. 2 is a simi lar view of a similar rheostat showing connection for an air compressing device, the resistance having been automaticall cut out. Fig. 3 is a similar view of a similar rheostat all of the resistance bein in circult. Fig. is a perspective view 0 a vacuum producing fan with electric motor for driving same and with one of our automatic rheostats operatively connected.

Throughout the several views similar reference numerals indicate similar parts.

The numeral 1 indicates a tube referably made of nomconductmg materi such These objects, together with other as glass, hard rubber, orcelain and the like, which tube is pre erably formed U shape, as shown in the drawings. The tube is arranged with the two arms of the U in vertical position and within one of the arms is arranged a vertical series of spaced contacts 2 each contact being connected with an appro riate binding post, screw, or other means 0 connection for an electric wire, as shown at 3 in the drawings. An electric conducting liquid 4 within the tube 1 entirely fills the lower curved portion of said tube and extends upward within the two vertically disposed arms a suiiicient distance so that when the said liquid is in the normal condition of equilibrium with reference to the two arms it will submerge the lowermost of the contacts 2 and will not be in contact with the next to the lowest of said contacts. For the liquid 4 we prefer to use mercury both because of its weight and conductivity. On top of the liquid 4 in both ofthe arms of the tube ties of a non-conducting liquid 5, pre erably mineral oil, constituting a iquid seal adapted to float upon the top of the heavier liquid 4 and seal the same'to prevent it from coming into contact with the air for the purpose of preventing oxidation or other deteriora-' tion of said uid 4 and to permit contact to be made an broken under said liquid.

It will be apparent that if pneumatic connection is made to produce air pressure in the upper portion of the arm of the tube which is not provided with contacts, that the liquid 4 in said tube will be forced upwardly in that arm of the tube .provided with contacts and will come into contact and submerge the said contacts from the bottom to the top of the series, in succession. The same result may be accomplished where the device is used upon a vacuum producing machine by connecting a portion of the machine in which the vacuum is created with the upper end of the arm which is provided with contacts. Such connection may be made by a small tube such as indicated by the numeral 6 in Fig. 1, which tube it will be noted is roperly arranged for use in connection with vacuum machinery whereas the tube 7 shown in Figs. 2 and 3 is properly connected for use with pressure creating machinery.

The numeral 8 indicates resistance diaammatically re resented as in circuit with e wires 9 and ii), and the wire 10 is pro/- are arranged uantivided with direct connection through the wire 11 with the lowermost contact in the tube 1 while the uppermost contact of said series is connected to the wire 12 which has no electrical connection with the resistance 8. The contacts in the vertical series intermediate the top and bottom contacts are connected to the resistance 8 at successive intervals as shown in the figures by the wires 11.

It will be apparent from an inspection of Figs. 1, 2 and 3 that when the liquid 4 is in the position of equilibrium shown in Fig. 3 and electric current is supplied to the circuit includin the wires 9 and 10, said current will be %orced to pass through the entire resistance 8. If now the liquid 4 be raised so as to come into contact withthe second contact in the vertical series the current will be shunted through said contacts and the intervening liquid 4, thus avoiding a portion of the resistance 8. If the liquid 4 be raised to the third contact more resistance will be avoided, and in this manner the resistance will be avoided to a greater extent as the liquid 4 rises within the tube and short circuits the contacts. When the liquid 4 has reached the uppermost contact of the series it will be well/understood that electrical connection will be made between the said uppermost and lowermost contacts of the series, as shown in Figs. 1 and 2.

In Fig. 4 we have illustrated a practical application of one of our automatic rheostats as applied to an air exhausting device. In said figure the numeral 13 indicates a fan of any well known construction having operative connection with a suction pipe 14 and adapted to produce a partial vacuum in said pipe 14, the air being driven out of exhaust pipe 15. An electric motor 16 is operatively connected to the fan 13. By way of example we have illustrated a shunt wound direct current motor adapted to be controlled by varying the strength of current passing through the armature. On the motor, binding post 17 is for one of the line wires, binding post 18 for the field supplying wire and blnding post 19 for the armature wire.

The numerals 20 and 21 indicate the two main lines supplying direct current, and 22 mdlcates the main line switch, of any well known construction. To one side of the switch 22 is connected the line wire 23 lead- 111? to the bindin post 17. From the same si e of the switch t ewire 24 leads to one end of a solenoid di ammatically represented at 25, from the ot er end of which the wire 12 leads to the uppermost contact of the ver-' tical series in the tube 1. To the other side of the switch 22 is connected the field wire 26 leading to the binding post 18 and to the same side of the switch is oonnected'thewire 9 leading to one end of the resistance 8 From the other end of the resistance 8 the wire 10, constituting the armature wire, leads to the binding post 19. From the wire 9 where same is connected to the resistance 8 the wire 27 leads to a contact 28 insulated from the spaced contact 29 which is connected to the wire 10 by means of the wire 30. An armature 31 arranged within the solenoid 25 is provided with a head 32 adapted for contact with the contacts 28 and 29 when the armature 31 is raised, to connect said contacts 28 and 29 in circuit. It will be understood that the solenoid 25, when energized, is adapted to raise the armature 31, as will be well understood by those skilled in the art. The tube 6 forms operative pneumatic connection between the suction pipe 14 and that arm of the tube 1 in which the vertical series of contacts is arranged and itwill be understood that as the air in the pipe 14 is rarefied the liquid 4 inthe tube 1 will be raised to short-circuit the contacts as hereinbefore described.

The apparatus illustrated in Fig. 4 having been provided, as described, the circuit for the armature wire 10 will normally lead through the resistance 8 at the time of starting, thus cutting down the current supply to the armature. As soon as the main line switch 22 is thrown to make connection with the lines 20 and 21, however, the motor 16 will be started and as it increases speed and the fan begins to rarefy the air in the pipe 14 the liquid 4 will begin to rise tosubmerge the various contacts within the tube 1 in succession, thus avoiding more and more of the resistance 8 and automatically supplyingl more and more current to the armature. W en the motor is so well started that the liquid 4 has been brought into contact with the uppermost contact of the vertical series the current will be shunted from the wire 10 through the liquid 4, entirely avoiding the resistance 8 and through the solenoid 25 to the wire 24. When this occurs the armature 31 will'be instantly lifted to close a circuitacross the contacts 28 and 29 and the armature wire 10 will then be supplied by current flowing directly from the wire 9 through the wire 27, contact 28, head 32,

.contact 29 and wire 30. This will avoid sendin the greater portion of the current througithe liquid 4 during the ordinary operation of the motor at full speed which is desirable, as readily understood by those skilled. in the art. When the motor is stopped by throwing out theswitch 22 the liquid 4 will return to the normal state of equilibrium illustrated in Fig. 3, and the armature 31 will drop, the solenoid 25 being no longer ener 'zed and the apparatus will then be in con ition for again starting the motor at an time desired, the entire resist'ance 8 being in circuit.

During the operation of the motor as the large number of cally varied in accordance with the requirements of the motor.

Attention should bcncalled to the fact that while we have shown the tube 1 of U shape we do not desire to be limited to such an exactconstruction, the essential features of the construction, being the spacedcontacts variously connected with the resistance and a conducting liquid adapted to short-circuit said contacts to avoid'the resistance, as described. Attention should also be called to the fact hat many other formsof electric motors and many electrical devices other than motors may be used in connection with our automatic rheostat, theapparatus illustrated and described being only one of a possible electrical arrangements. It should also be noted that while in this specification our invented iheostat is describe'd as especially adapted for the control of pneumatic devices and as controlled by pneumatic action, the device is equally applicable to cases where liquid, vapor or gas is compressed or rarefied, and the device may be operated by liquid, vapor or gas as well as by air. In the claim hereunto appended, where the words air and pneumatic are employed, the same shall be interpreted as including liquid, vapor and gas.

We claim A rheostat comprising in combination with a main circuit, resistance. arranged in said circuit, a series of spaced contacts tapped into said resistance at intervals, a conducting liquid, means forming constant electrical connection between said liquid and said circuit at one side of said resistance, means for pneumatically actuating said liquid to bring the same into successive contact with said contacts and electrically operable means connected with the last contact of said series for losing a shunt circuit around said resistance and liquid when said liquid contacts with said last contact.

In testimony that we claimthe above, we

have hereunto subscribed our names in the presence of two witnesses.

HENRY M. GROSSMANV JOHN WYNN, JR.

Witnesses:

- JOHN H. BISHOP,

WILLIAM H. MILLER. 

